title: Effect of ammonia on calcium homeostasis in primary astrocyte cultures.
abstract: Calcium influx, accumulation and efflux were studied in primary cultures of rat astrocytes treated with ammonium chloride. Treatment of the cells for 3 days with 10 mMN4Cl resulted in a 35% reduction in 45Ca influx. The decrease in calcium influx was dose-dependent between 2 and 10 mM NH4Cl. Short-term (30 min) exposure to ammonia had no effect on calcium influx. Calcium accumulation, as measured by 20-min exposure to 45Ca, decreased after treating cultures with 10 mM NH4Cl for one or 3 days; a greater effect was observed after the 3-day treatment. Studies with lanthanum, an inhibitor of calcium transport, indicated that the effect of ammonia was not due to non-specific leakage of calcium. Calcium efflux was not affected by exposure of the cultures to ammonium chloride. Purinergic-evoked calcium influx and mobilization was not altered by ammonia. While the mechanism(s) of calcium homeostasis affected by long-term hyperammonemia remain to be defined, these results suggest that reduced astrocytic calcium may be related to the pathogenesis of ammonia-related disorders such as hepatic encephalopathy.
authors.affiliation: Laboratory of Neuropathology, Veterans Administration Medical Center, Miami, FL 33125.
authors.forename: J T
authors.initials: JT
authors.lastname: Neary
authors.forename: C
authors.initials: C
authors.lastname: Woodson
authors.forename: J
authors.initials: J
authors.lastname: Blicharska
authors.forename: L O
authors.initials: LO
authors.lastname: Norenberg
authors.forename: M D
authors.initials: MD
authors.lastname: Norenberg
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000643:Ammonium Chloride / Q000494:pharmacology*; D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000378:metabolism; D006706:Homeostasis / Q000187:drug effects; D007700:Kinetics; D007811:Lanthanum / Q000494:pharmacology; D051381:Rats
chemical_list: D000643:Ammonium Chloride; C028521:lanthanum chloride; D007811:Lanthanum; D000255:Adenosine Triphosphate; D002118:Calcium